Artist Jay Nelson is drilling the sofa bed drawers in a tree house in Marin - last-minute touches before he flies out to build a 200-square-foot cabin in the lush north of Kauai.

Homeowner Daria Joseph carries up local bread with fig preserves and Parrano cheese. The 25-step spiral staircase outside has just been attached, and she's delighted by this first chance to entertain. "I just can't believe this is mine," she says. "As you can imagine, there is a long list of people who want to climb up here."

For Joseph, 63 - a ceramist who is the granddaughter of Erich Mendelsohn, a famed modernist architect and collaborator with Einstein - this tree house marries her fascination with design and childhood. (Her collection of 350 Pez is displayed above her Moroccan sofas and her refrigerator is etched with a story about her mother's brown fridge.)

For Nelson, 34, who is also a painter, the fascination is creating a small space: "There is something really optimistic about the simplicity of less stuff and only having what you need." He loves to work without a blueprint literally starting with one plank of wood in his hand: "You work around the tree, so it grows like that. Building a tree house is like taking a photo or making a painting. The way you orient everything, such as where you put the windows, you are directing people's vision, their experiences - that's a very exciting thing."

A mod hippie vibe

Every part of the tree house reveals considered artistry with a mod hippie vibe. Six bolts fasten the tree house to two redwood trees and it's also cantilevered. Inside, the 10-by-12-foot room and a loft feature his signature reclaimed wood, geometric ceilings and stained glass portals as well as three large windows looking over the rooftops. The cream canvas cushions on the sofas have been hand-dyed by his friend Matt Katsaros using bark from the trees and the throw pillows and blanket are tie-dyed indigo - the best of Bay Area crafty cool.

This is Nelson's fifth tree house, but he started making pretty elaborate hideouts when he was just 10 years old, a young surfer living in Redondo Beach (Los Angeles County). No wonder; his father was a USC physics professor and inventor. He learned the history of surf shacks, shaping his own with driftwood, concrete and palm fronds and he built patios into beach cliffs.

Tree house in Hawaii

After he was diagnosed with cancer at age 14, he was homeschooled by his mother and spent hours drawing, painting and doing ceramics. After completing a bachelor's in fine arts at California College of the Arts he left for Hawaii to build his first tree house, using hand tools and material found on the beaches and forests. When he came back to San Francisco to do a show of his paintings at Needles & Pens store, he made another tree house using recycled urban stuff and lived there for a month.

Pushing his minimalist ideals and working with what was on hand, he built a camper shell over his Honda Civic and lived and traveled in it extensively, including to New York where he completed his master's in fine arts at Bard College. Though the camper attracted a lot of attention and goodwill, he realized eventually that living that small was not a freedom after all. "But it was necessary to go through those five years of my life where I didn't pay rent."

You might have seen Nelson's structures - a tree house, bike, car and boat - at Mollusk Surf Shop (where he lived for a while, too) in the Outer Sunset. He's also built out two motorboats and six vehicles, including a Toyota as Artist In Residence at Facebook.

Nelson lives just around the corner from Mollusk with his wife, sculptor and painter Rachel Kaye, and their 3-month-old baby, Romy. He's currently remodeling the 750-square-foot ground floor of the duplex they own with friends and he's building a studio out the back. Not surprisingly, the place has an artsy beach cabana feel with succulent gardens, an outdoor shower and his 15 surfboards stacked at the side.

Everywhere, timber is piled high: finding beautiful old wood is his obsession and he spends much of his day driving to building sites. His wife quips that is actually his job.

"He gets a call from someone who has old wood, and he can never turn it down. I joke that he's a wood hoarder. A lot of people think new is better but Jay knows that old wood comes from bigger trees and is grainier and has a history. He has a gift for finding good things that are special and beautiful and often free."

Tree houses are not something he wants to do all the time. He turns down a lot of work because he aims to build a relationship that will last forever - he and his family have become like family to Joseph. Also the cost: tree houses cost a minimum of $25,000.

Nelson packs up his tools, ready to head home to look after baby Romy, walk his dog Johnny and finish packing for Hawaii. There are so many projects to think about, including a traveling repair center for Patagonia and his new passion, making rooms to display art: "There is no division between my life and my work. I suppose in that way I don't think of it as work. It's how I am and I'm happy with that."

Tree houses

Rules for building a tree house vary by city. In some, they are not allowed to be an extension of a home; cannot be a studio space or for storage; not more than 120 square feet, higher than 15 feet off the ground and must be a structure built for a child. In San Francisco, the building codes are silent about tree houses, according to the Department of Building Inspection, but any structure larger than 100 square feet requires a building permit.